1. Field of the Invention
The present invention relates to improved methods for manufacturing optical fiber ribbons that are produced by arranging optical fibers side by side in the same plane and coating them with a coating resin integrally, as well as a separable optical fiber ribbon that is produced by arranging the optical fiber ribbons side by side in the same plane and coating them integrally with a coating resin.
The present invention particularly relates to an alignment guide having a special structure that is adapted to produce optical fiber ribbons and a separable optical fiber ribbon thereof by a stable and uniform coating operation. The present invention also relates to an improved apparatus and method for producing optical fiber ribbons and a separable optical fiber ribbon thereof using the alignment guide.
2. Description of the Related Art
FIGS. 6A and 6B are schematic views of a conventional art mechanism for aligning optical fibers in producing an optical fiber ribbon.
FIGS. 7A and 7B are schematic views of another conventional art mechanism for aligning optical fibers in producing an optical fiber ribbon.
In FIGS. 6A to 7B, numeral 40 represents an optical fiber; 41, an optical fiber supply unit; 42, a coating applicator; 43, an optical fiber; 44, an optical fiber gathering device; 45, optical fiber gathering rollers; 46, a groove; 47, an alignment guide roller; 48, a concave; 49, a supply bobbin; 50, a curing device and 51, a turn roller.
As shown in FIGS. 6A and 6B, Unexamined Published Japanese Patent Application (kokai) No. Hei. 10-142464 discloses that a plurality of optical fibers 43 are passed through the optical fiber gathering device 44 consisting of optical fiber gathering rollers 45 each having a groove 46 in the rim. As a result, the individual optical fibers are spaced apart in a plane without problems such as irregularities in optical fiber arrangement and damage to optical fibers.
In this case, because of the existence of the coating applicator 42, the distance between the optical fiber gathering device 44 composed of rollers 45 with the grooves 46 spaced apart and the turn roller 51 cannot generally be made short enough to ensure suppression of vibrations of optical fibers, which tends to cause "planer eccentricity" as defined later.
As shown in FIGS. 7A and 7B, Examined Published Japanese Patent Application (kokoku) No. 8-33507 discloses that an optical fiber aligning apparatus is adapted to have a vertical pass line and optical fibers 40 are aligned with a plurality of alignment guide rollers 47 each having the concave 48 in the rim. In the case shown in FIG. 7A, three of such alignment guide rollers are provided at different positions in contact with optical fibers.
The apparatus has a disadvantage that each alignment guide roller 47 tends to costrain all optical fibers laterally toward the center thereof, thereby causing the optical fibers to contact each other.
If adjacent optical fibers contact each other before they enter the coating applicator 42, mutual friction develops to increase the chance of the occurrence of vibrations. If the individual optical fibers 40 are not sufficiently wound onto the alignment guide rollers 47 but are placed in partial contact with them, one of the optical fibers before they are integrated into a fiber ribbon is likely to be subjected to a great torque causing the alignment guide rollers 47 to rotate. As a result, the tension on that particular optical fiber 40 increases under reaction force but the force is not stable, therefore the optical fiber is likely to vibrate.
The upset in the balance among the tensions on the individual optical fibers 40 also causes differences in length between the optical fibers 43 and otherwise deteriorates their characteristics.